Preben Soeberg wrote:
I guessed the chroma 4 is much like the Eye One Display as it was originally a OEM variant of the Chroma 4.
Yes, I understand it's something like that.
So, in i1disp.c, I changed the code to look like this At the top of the file static boolean chroma4 = FALSE;
This should go in the _i1disp structure in i1disp.h after lite".
At line 1100: if (ver < 5.1) { vv = 'L'; chroma4 = TRUE; } if (ver >= 5.0 && ver <= 5.3 && vv == 'L') {
It would be better if you said what the version number and sub type (vv) the chroma 4 is, so that it could be recognized correctly, rather than faking an i1disp1, and this means I could investigate how this instrument should be treated (or not).
At line 1300: /* RGB channel scale factors */ for (i = 0; i < 3; i++) { double tt; tt = (double)p->reg44_S[i] * 1e11/((double)p->reg40_S * (double)p->reg42_S); if (chroma4) tt *= 4; // Multiply white level reading with 4 to be more correct The last hack was made to give white level around 140 Cd/m^2 using dispcal -yl -r. This also gives correct reading for maximum brightness according to monitor specifications.
It's hard to justify this unless you've got another instrument that you trust to compare it with though. (ie. the monitor specs could be quite different to the actual monitor behaviour). The right spot for an absolute scale factor is in i1disp_take_XYZ_measurement().
It works like a dream, though I cannot rely on the absolute value of gamma. Setting -g1.75 in dispcal gives a final gamma of 2.2 (according to my gamma swatches, downloaded from Timo Autiokari).
It's probably more reliable to check for yourself using dispwin and spotread. Read the Y for 100% and 50%. Gamma = log(50%Y/100%Y) / log(0.5)
I'm leaving Nvidias settings from installation time untouched. I do not understand the black point setting, as I see it in the calibration file: BEGIN_DATA 0.0000 0.019102 0.018301 0.017533 3.9216e-003 0.025279 0.024478 0.024011 7.8431e-003 0.031338 0.030534 0.030370 I don't understand why is it not going down to more near zero.
It doesn't necessarily follow that zero device value is the threshold where the display starts to turn on. Some devices have a dead zone from zero where nothing happens, so it's important to set the calibrated zero at the threshold where something starts to happen, otherwise the display characteristic isn't invertible, and a calibration curve can't be created. Having said that, it doesn't mean that I think the current calibration algorithm is perfect in what it achieves for the black point. Thanks for the feedback on the Chroma 4 - I'll see about adding your changes into the code, if you can clarify what the actual version number and sub-model ID is. Graeme Gill.